A Concord man was found guilty of involuntary manslaughter and two other felonies Friday after his three pit bulls fatally mauled his 2-year-old stepgrandson in the garage of their Concord home in 2010.

Steven Hayashi was also convicted of child endangerment and owning a mischievous animal that kills a human. He faces up to 10 years in prison in connection with the death of Jacob Bisbee at the family's home on Trailcreek Court.

Judge John Kennedy of Contra Costa County Superior Court issued his verdict in Martinez after a bench trial, meaning there was no jury. Hayashi, 55, will remain free until his June 13 sentencing.

Kennedy noted that Hayashi had ignored "daily pleas" by his wife and Jacob's father to remove his five dogs, all pit bull mixes, from the home the extended family shared.

"I find a reasonable person would not permit a child to be exposed to that danger," Kennedy said.

Defense attorney David Cohen said he was disappointed but not surprised by the verdict. He said outside court that he hoped the judge would recognize that "with all the tragedy that this family has suffered, that Mr. Hayashi should not go to jail."

On the morning of July 22, 2010, Hayashi was designated as the caretaker for Jacob and his brother, who was 2 years older - the usual practice while his wife slept after a night shift.

But Hayashi went out to play tennis with his son, leaving Jacob and his brother unsupervised, said Contra Costa County prosecutor Mary Knox.

She said Hayashi did not lock the door to the garage, telling police later that while the boys could open the door, they usually stayed in their room. Jacob wandered in, though, finding Sadie and her pups, Kiwi and Jake. Hayashi's two other pit bulls were in the backyard.

In a 911 call that was played during the trial, the screams of Hayashi's wife are heard in the background as she discovers Jacob. Asked if the boy was breathing, Leticia Hayashi said no.

In a jailhouse interview with The Chronicle a day later, Steven Hayashi said he didn't believe he was "totally responsible" for Jacob's death, but acknowledged that he had ignored warning signs, including when one of his dogs killed his Chihuahua.

Before the tragedy, Hayashi said he had always believed that pit bull owners - and not the dogs themselves - were the problem.

"Well, I used to think that way," he said. "That's what got me into this mess, just thinking they're regular dogs. I can understand a dog biting or nipping, but to maul somebody until he's dead?"